Young people have been subjected to the highest concentration of Jewish propaganda as they spend they entirety of their day devoted to indoctrination, conversing with other indoctrinated children, and then going home to watch Jewish propaganda, where they're subjected to emotional abuse and Pavlovian training, in what is quite literally a psyop. The emotional abuse they've suffered makes them violent zealots of their abuser's – Jewish media's – ideas, to spare themselves another round of emotional abuse – social ostracization, humiliation, assertions of moral failing and worthlessness, among other things.
They don't think they're smart because the think the politics are smart, they think they're smart because of the psyop. Because Jews have subtly screamed at them though their media that they're STUPID STUPID STUPID WORTHLESS RACIST IDIOT HORRIBLE FAT COW SEXIST BAD PERSON BAD PERSON BAD PERSON and then the nice Jew showed them someone who disagreed with Jewish politics and said, "Wow, aren't they stupid, guys?" and audience laughed, and the child laughed too, and now the child wasn't being called stupid, or worthless, they were laughing with someone, they were smart, people agreed with them, they weren't being hurt any more, they were being pet, and they realized that they too were leftist, and went on to perpetuate the abuse onto the other children to stop their own.
They also have the least real world experience to uproot the lies they've been fed, and the least opportunity to encounter anyone who could teach them truths or help them undo their conditioning. They make perfect Democrat voters.